Index: Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Plugin/FileImporters/HeightStructureUpdateDataStrategy.cs
===================================================================
diff -u -rf21dfc68719af2540c7c07392fdd3d045907098d -r8980db4ffba26defbde335c001e559f1e8d0c1d0
--- Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Plugin/FileImporters/HeightStructureUpdateDataStrategy.cs	(.../HeightStructureUpdateDataStrategy.cs)	(revision f21dfc68719af2540c7c07392fdd3d045907098d)
+++ Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Plugin/FileImporters/HeightStructureUpdateDataStrategy.cs	(.../HeightStructureUpdateDataStrategy.cs)	(revision 8980db4ffba26defbde335c001e559f1e8d0c1d0)
@@ -123,10 +123,9 @@
                 }
             }
 
-            affectedObjects.AddRange(StructuresHelper.UpdateCalculationToSectionResultAssignments(
-                                         FailureMechanism.SectionResults,
-                                         FailureMechanism.Calculations.Cast<StructuresCalculation<HeightStructuresInput>>())
-            );
+            StructuresHelper.UpdateCalculationToSectionResultAssignments(
+                FailureMechanism.SectionResults,
+                FailureMechanism.Calculations.Cast<StructuresCalculation<HeightStructuresInput>>());
 
             return affectedObjects;
         }
Index: Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Plugin.Test/FileImporters/HeightStructureUpdateDataStrategyTest.cs
===================================================================
diff -u -rf21dfc68719af2540c7c07392fdd3d045907098d -r8980db4ffba26defbde335c001e559f1e8d0c1d0
--- Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Plugin.Test/FileImporters/HeightStructureUpdateDataStrategyTest.cs	(.../HeightStructureUpdateDataStrategyTest.cs)	(revision f21dfc68719af2540c7c07392fdd3d045907098d)
+++ Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Plugin.Test/FileImporters/HeightStructureUpdateDataStrategyTest.cs	(.../HeightStructureUpdateDataStrategyTest.cs)	(revision 8980db4ffba26defbde335c001e559f1e8d0c1d0)
@@ -453,13 +453,11 @@
             // Assert
             AssertHeightStructures(readStructure, structure);
 
-            var expectedAffectedObjects = new List<IObservable>
+            CollectionAssert.AreEqual(new IObservable[]
             {
                 failureMechanism.HeightStructures,
                 calculation.InputParameters
-            };
-            expectedAffectedObjects.AddRange(failureMechanism.SectionResults);
-            CollectionAssert.AreEqual(expectedAffectedObjects, affectedObjects);
+            }, affectedObjects);
 
             sectionResults = failureMechanism.SectionResults.ToArray();
             Assert.AreEqual(2, sectionResults.Length);